The United Nations says more than 1,000 people were killed in Iraq in May, making it the country’s deadliest month since 2008.

The data from the U.N. Assistance Mission for Iraq, released Saturday, said another 2,400 people were wounded since the end of April, and said nine out of 10 fatalities were civilian. Mission chief Martin Kobler described the new figures as “a sad record,” and demanded an immediate end to what he called “this intolerable bloodshed.”

More than 1,700 people have been killed in the past two months, further stoking fears of all out sectarian war as resurgent al-Qaida and Sunni fighters challenge the Shi’ite government of Prime Minister Nouri al-Maliki.

Analysts say the Sunni armed groups appear invigorated by the Sunni-led revolt in neighboring Syria, where rebels are seeking to topple the government of President Bashar al-Assad. There have been numerous reports of Iraqi fighters from both sects crossing the border to fight in Syria’s civil war.

Sectarian violence in Iraq peaked in the mid-2000s, following the 2003 U.S.-led invasion aimed at toppling Iraqi leader Saddam Hussein. At the height of the violence, the monthly death toll sometimes topped 3,000.